This invention relates to disc phonograph players and more particularly, to a pickup arm device of the disc phonograph player.
In order to ensure arbitrary vertical movement of an arm of pickup arm devices, it is the general practice to use a pivot mechanism in which pivots secured to a pivot holder are supported by pivot bearings. The superiority in operation of the pickup arm has ordinarily been evaluated by the sensitivity of the pickup arm. This is represented by a minimum load (mg) with which the arm can operate when loads are applied to the tip of the arm. The sensitivity of the arm is greatly influenced by the contacting force of the tip of the pivots exerted on the pivot bearing. Smaller contacting forces result in sharper sensitivity of the arm, thus improving the traceability to record grooves.
The pivots have heretofore been fixed by a method in which screw pivots are set in a pivot holder from opposite sides thereof so as to be pivotally supported by a pivot bearing and then fixed by means of lock nuts. However, this fixing method involves the problem that it is difficult to directly control the contacting force of the screw pivots exerted on the pivot bearing, so that the contacting force must be indirectly controlled by the use of the torque at the time of the setting of the screw pivots, and thus even though the torque is held constant, a true contacting force may vary owing to differences in accuracy of parts, leading to the scattering in sensitivity of the pickup arm. Further, even though a lock nut is employed, the screw pivots will loosen when mechanical vibrations are applied over a long time with the attendant disadvantage that there is a tendency for the pivots to become loose relative to the pivot bearing.